Crowd density piece of sand by piece of sand

Counting isn’t asked for in words: it’s drawn. There’s a line across the way in from the boardwalk — whatever crosses it gets added up — and four zones drawn over four different pieces of sand. Inside each zone IRIS counts the people and divides the square footage of that piece by how many are in it: that’s how much room each person has. Neither the line nor the zones fit in a sentence; they have to be drawn onto the frame, following the exact edge of each piece. That’s why counting is set up by drawing and searching is done by talking. And that’s why the figure is repeatable and auditable: the line and the zones are always in the same place.

Capacity is how many people are on the whole beach. Density is how much room each of them has in a given piece of it, and the two aren’t the same thing and aren’t good for the same thing. A beach can sit at forty percent of capacity and still have its way in impassable, with people turning sideways to get between the towels. The capacity figure doesn’t show that; the figure for each piece does. With the four zones drawn, whoever runs the beach knows where to put one more lifeguard, which of the two ways in to open and when it’s worth saying something over the PA — and can explain why to whoever asks. IRIS people counting is approved by the Centro Español de Metrología, Spain’s national metrology institute: that the figure is the right one is vouched for by an independent third party, not by us. That approval is Spanish and it isn’t equivalent to any U.S. certification. It covers that one measurement — people counting — and not the whole product.